The pupil

PURPOSE OF REVIEW: To give an overview on topics of pupillary function selected according to their relevance in clinical neurology. Mainly publications of the last 3 years have been considered. RECENT FINDINGS: The discovery of photosensitive retinal ganglion cells not serving vision, but serving circadian rhythm and the pupil initiated many studies. There is evidence that pupil reaction to light might be preserved even if all rods and cones are lost. Spontaneous pupillary contractions in darkness occur in sleepy subjects and have been used to quantify the state of alertness. Apraclonidine eye drops have been suggested to diagnose Horner syndrome. Iatrogenic cause and carotid artery dissection are the most frequently reported underlying causes of Horner syndrome. Anti-Hu antibodies may be associated with tonic pupils. SUMMARY: Pupil studies in blind patients may give new insights into the function of the pupillary system. Testing for sleepiness by means of pupillography might be used more frequently. Testing for Horner syndrome still needs to be done with cocaine eye drops. Clinical evaluation has to be focused on detecting additional signs and symptoms. Unknown malignancy is very rare. In the tonic pupil (Adie syndrome) autoantibodies may play a role, in exceptional cases it might represent a paraneoplastic disorder.     

The pupil and vigilance

Pupillary size and activity are dependent upon the physiological state of the organism, including vigilance. Measurement of pupillary size and responses to drugs as used in the study of these states are reviewed. These tests can be employed for the diagnosis of narcolepsy and for monitoring drug effects.     

The pupil and its disorders

Pertinent information concerning the pupil is provided for the practicing and aspiring neurologist, including anatomy and physiology of the normal pupil, a discussion of pupillary disorders, and unusual pupillary abnormalities.     

The Marcus Gunn pupil.

BACKGROUND--Palatal tremor is divided into symptomatic palatal tremor (SPT) and essential palatal tremor (EPT) on the basis of clinical features. The inferior olive seems to be abnormal in SPT, but not EPT. Because the inferior olive is likely to be involved in several types of motor learning, it is hypothesised that motor learning would be abnormal in patients with SPT, but not those with EPT. METHODS--In six patients with SPT and four patients with EPT, two motor learning paradigms were studied--the classical conditioning of an acoustically elicited eyeblink with electrical supraorbital nerve shock and a test of adaptation of ballistic arm movements to a change of the gain. RESULTS--Classical conditioning was impaired unilaterally or bilaterally in the patients with SPT, depending on whether they had unilateral or bilateral abnormalities of the inferior olives, except for the two least affected patients. All but one of the patients with EPT had normal conditioning. On the adaptation test of arm movements, most of the patients with SPT had impaired learning of the arm contralateral to the hypertrophied inferior olive, regardless of whether the abnormality was unilateral or bilateral, but all patients with EPT had normal results. CONCLUSIONS--In SPT pseudohypertrophy of the inferior olive leads to defective cerebellar function, whereas in EPT the inferior olive functions normally.     

The opposite pupil in herniation

I serially examined the pupil opposite the one already enlarged from transtentorial herniation in 13 patients. The main abnormalities, stereotyped in most patients, were an initially diminished light reaction with a 2.5- to 4-mm-diameter pupil, followed by slight reduction in size, and then reenlargement to greater than original size, all with preserved roundness. Subsequent deterioration varied among patients, but a transitional oval shape was infrequent and oculomotor function was preserved until both pupils were enlarged and fixed. Once the pupil on the side of a mass enlarges, heralding herniation, subsequent deterioration can be appreciated through changes in reactivity and size of the opposite pupil.     

The pupil and myself: pupil dilation during retrieval of self-defining memories

Neurological Sciences - There is a recent interest in pupil dilation during the retrieval of autobiographical memory. We pursued this line of research by measuring pupil diameter during the...     

The dilated pupil: An update

The dilated pupil can present a significant challenge to the clinician. Although in most cases a complete history and physical examination is sufficient to make an accurate diagnosis, selected patients will require further investigation, including pharmacologic testing and neuroimaging. This review outlines the physiology, clinical features, and diagnostic approach to the most important causes of the dilated pupil. Particular attention is given to recent publications on this topic.     

Apraclonidine and my pupil

Purpose  

Used in the diagnosis of Horner’s syndrome, apraclonidine 1% dilatates the involved eye due to denervation supersensitivity. Recent literature suggests that in healthy volunteers, apraclonidine provokes a mild miotic effect. Since the comparison of both the pathologic and the non-pathologic eye is important, we wanted to further investigate the effect of apraclonidine on the healthy eye. By measuring the effect on the pupil intermittently over a few hours, we tried to determine the best moment for evaluation after instillation with apraclonidine. Therefore, the effect of apraclonidine on pupillary parameters was investigated in 14 healthy volunteers.     

The Behr pupil revisited. Anisocoria following cerebrovascular accidents.

Three hundred and sixty-three cases of cerebral infarction were reviewed: 19 had anisocoria. Eighty percent had the larger pupil contralateral to the hemispheric lesion. The mydriasis was associated with long tract signs in all instances. If the abnormal pupil and long tract signs are not on the same side, the long tract signs are the most accurate evidence of the side of thhe hemispheric lesions. When the pupil was 4 mm or larger and reacted sluggishly, the prognosis was poor. The mechanism of the production of the anisocoria is still uncertain; the lesion is probably "cortical" and in the contralateral hemisphere.     

The post illumination pupil response is reduced in seasonal affective disorder

Individuals with seasonal affective disorder (SAD) may have a decreased retinal sensitivity in the non-image forming light-input pathway. We examined the post illumination pupil response (PIPR) among individuals with SAD and healthy controls to identify possible differences in the melanopsin signaling pathway. We also investigated whether melanopsin gene (OPN4) variations would predict variability in the PIPR. Fifteen SAD and 15 control participants (80% women, mean age 36.7 years, S.D.=14.5) were assessed in the fall/winter. Participants were diagnosed based on DSM-IV-TR criteria. Infrared pupillometry was used to measure pupil diameter prior to, during, and after red and blue stimuli. In response to blue light, the SAD group had a reduced PIPR and a lower PIPR percent change relative to controls. The PIPR after the blue stimulus also varied on the basis of OPN4 I394T genotype, but not OPN4 P10L genotype. These findings may indicate that individuals with SAD have a less sensitive light input pathway as measured by the PIPR, leading to differences in neurobiological and behavioral responses such as alertness, circadian photoentrainment, and melatonin release. In addition, this sensitivity may vary based on sequence variations in OPN4, although a larger sample and replication is needed.